The present invention relates to electrical or electronic apparatus.
It is well-known that the expected life-time of electronic apparatus is very dependent on the temperature to which the apparatus has been subjected. For example, the expected life-time of semi-conductor based products may be halved for each prolonged rise in temperature of approximately 10 to 20.degree. C. It is possible to formulate theoretical expectancy equations which relate the expected remaining life-time against time already operated at a certain temperature, from which estimates for the expected failure for the product can be established. However such equations are only valid on a large population, so for a user of only a few pieces of equipment it is not feasible to use this approach.
The present invention provides electrical or electronic apparatus characterised by means to determine in which of a plurality of predetermined temperature bands of differing size temperature ranges the apparatus ambient temperature is and means to record outputs of the determination means.
In this way, there is produced a record of the degree of stress to which the apparatus has been subjected and so allows the user to have an indication of how the life-time of the product has been shortened. By having temperature bands of differing sizes, careful and accurate monitoring of temperature regions of particular interest can readily be achieved. In one example, size of a band decreases with increased temperature.